Sprockett

OK, I noticed a little while ago when I was installing my intake that the clamp by the y-pipe coupler was stripped, and would not tighten very much. Well, several weeks later while driving I heard a huge air wooshing sound, and figured that the y-pipe had come loose. I was correct, and bought a new set of clamps the next day. However, while fixing that, I found that there was a bunch of oily residue by my intake, right by my BOV. I have been quite skeptical of that BOV for a while because it seems like it needs a lot of throttle to get it to close and keep the boost pressure in. Basically, what I mean is, if I don't push down hard on the gas most of the boost will rush out through the BOV. I figure that the spot of oil by the valve proves that this valve has gone bad, so all I need is someone to confirm this before I order the Blitz DD BOV tomorrow. Am I right? Also, how much louder is the Blitz DD BOV compared to an open-air vented stock BOV? (Like 2 times, 1.5 times, etc.)

911GT2

If you don't push down hard on the gas most of the boost SHOULD vent through the BOV. What do you mean by hard, on the floor?

Either way, you should have low boost at part throttle, full boost should only happen in its normal pattern at WOT.

paw140

Wait... I thought a blowoff valve only opened when you *closed* the throttle, to vent off pressure spikes. You are saying your BOV is venting at low throttle? Sounds messed up to me.

Sprockett

That's right, and I am sorry that I ended up posting this 3 times........the site was slow, so I clicked on the button a couple of times to see if it had just stalled.

See, that's what I was thinking, too - It'll vent all the way up to 3k if I don't push the pedal down more than 50%. Sounds like a freaking jet engine on startup, too - with the AWS. Air shoots out of that thing like crazy. I am thinking that it got f'd up when the dealership connected it wrong, sending all the boost out of the BOV all the time. I think I'll just replace it anyway - it'll look nicer with the DD than the brown plastic thing. Hopefully it will be louder, too, because I love that BOV sound.

duboisr

The stock valve is opened with a small amount of vacuum and at idle it is open ,and when you let off the gas at higher rpm . If the valve is sticking it may be open longer than others . These things open so easy you can suck on the nipple and it will open , they are *****, right .My mechanic is going to put a heaver spring in one to see if it will stay closed during idle,and open at high rpm let off when the vacuum is greater. That way low speed will improve.

Mahjik

iTrader: (1)

Yes, the stock BOV doesn't have a strong spring like aftermarket BOV's (which is a nother reason not to vent it to atmosphere).

So at idle or mild acceleration, it will vent air. Under hard acceleration, it will close to allow boost to build until it's time to vent it again.

Lost Time

What you're experiencing is normal, it will vent boost whenever there is vaccum in the manifold. It only closes up when the manifold sees 0psi or above.

Sprockett

But what about all the oily residue right in front of the opening?

maxpesce

I think you are confusing the BOV and the CRV, the BOV should only VENT BOOST on Closed throttle /Overrun conditons to prevent COMPRESSOR SURGE - under VACCUM condition it may (but is not really supposed to) open and SUCK air (NOT VENT). it is NOT used to control BOOST. The CRV will be OPEN to vent second turbo boost at LESS than 4000 rpm and during Prespool, it (the CRV) will close during Transition and remain closed as long you under BOOST conditions and over 4500 rpm. MY CRV vents very noticably at part<>full throttle between 3k & 4k rpm, makes a sort of low bass Sax kind of sound

maxpesce

The oily residue is a combination of oil that leaks past the Compressor side turbo oil seals, and oil mist from the PCV system that vents into the primary turbo intake elbow, because its under vaccum even during positive BOOST conditions (during manifold vacuum conditions the PVC vents to the UIM down stream of the TB)